I went to restart my machine tonight and it popped up with a warning saying "other people are connected to my file sharing". I have 2 machines but the other one is shut down and I can not see it in my list of computers that pop up with they are connected or my machine can connect to.

How do I see who is connected to my machine? I am worried since the machine is on the web that some one in the world is leaching files from my machine. How can I find out?

Open Server Admin and click on AFP and then 'Connections' to see who is connected to Apple File Service. You will probably find that some are Asleep/disabled. Also check under SMB to see who is connected as a windows user.

Thanks. Maybe I posted this in the wrong area. I just have a normal G5 tower. I am not running a server so I don;t know how to get to the Server Admin? Can I access that from my normal computer or do I need special server software?

Not too sure how you tell then. I am sure its possible via terminal and you might see it in Network Utility running Netstat. If I connect another machine to this I get a line in Netstat that says this:

tcp4 0 0 192.168.1.102.afpovert 192.168.1.100.50000 ESTABLISHED
and this one too:
tcp4 0 0 192.168.1.102.52839 192.168.1.100.afpovert ESTABLISHED

102 is the address of this machine and 100 is the address of the connecting machine.